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| Sanderling |
The varying migration choices made by different birds I’ve seen recently has made me ponder the pros and cons of the various strategies they adopt.
Most, if not all, life has one overriding driver, to produce viable offspring and hence perpetuate the gene line. Pretty much all bird behaviour derives from this one simple driver. Different birds adopt different tactics to deliver this, the key being how to be in prime condition when it comes to breeding season in order to attract a mate and successfully raise their progeny. Condition is largely determined by food supply and energy usage, put simply the question is how to consume the maximum amount of food while expending the minimum amount of energy. In northern climes there are two basic choices in winter. Firstly, stay put, save energy and hope there is enough food to see you through the winter. Secondly, expend a lot of energy migrating to warmer climes but hence ensuring abundant winter food. The other part of the equation is ensuring there is abundant food for your offspring when and where you choose to breed. It’s natures complicated equation but evolution has a simple answer, those that do it best survive, those that don’t die out. It was all pretty straight forward until man came along and started messing with the equation through his vandalism of the environment.
Change is happening fast. Historically for insect eaters in northern Europe it was a fairly straightforward choice, come north to breed for the long warm days of spring and summer when there was an abundance of insects then return south in the winter or starve. There were a few exceptions. Dartford warblers are insect eaters at the very limit of their range in the south of England and somehow survive the English winter on the slim pickings of spiders and other insects deep within the gorse. They were always at the mercy of a cold winter which would decimate their numbers.
As man-made climate change has driven warmer winters the equation has changed quite dramatically. Chiffchaffs are a case in point. Until recently they always migrated but now a few stay and run the risk of overwintering in the UK. The reward lies in putting their towels down on the prime terrotories, start breeding earlier and save the energy cost of the travel ticket from the south. The stay put strategy will win as long as more of your offspring survive relative to those that migrate. The maths is simple. Let’s for the sake of argument say that Chiffchaffs that overwinter here on average produce 10% more viable, i.e they live to breed themselves, young than those that migrate. Let’s further arbitrary say that the current population is currently split 1% stayers, 99% migrators. In 25 years the stayers will dominate the population, will outcompete the leavers for food supply and the leavers will die out – evolution in action driven by a little added climate change from man.
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| Sanderling |
It’s been a wonderful spring for migrating Sanderlings in Oxford. These small clockwork toy like waders adopt an extreme migration strategy. The majority overwinter in Southern Europe and Africa where there is an abundance of food. In the spring they migrate to the high Artic to utilise the endless daylight and food supply of insects and plant material to raise their brood of three to four chicks. I love their old name of Sand Ploughman from where their modern name comes. We have had Sanderlings on the shores of Oxford water bodies in all states of moult into breeding plumage ranging from a not unattractive near monotone black and white to my personal favourite of a bold rusty red. I had assumed that the monotone ones were simply moult laggards but my black belt birding neighbour Mick told me that it was though that only some adopt the full costume change to breed. Presumably, evolution will eventually favour one strategy over the other and the winner will dominate. For example females may prefer the brightly coloured males but they might be more prone to predation, its down to life’s equation as to who wins out yet again.
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| The Collared Pratincole curtesy of my good mate Nick Truby |
I will confess that I have done one twitch recently since the relaxation in travel restrictions to see a vagrant Collared Pratincole on the Severn Estuary near Bristol. I have seen one of these very attractive bids before in the UK in Wales a couple of years ago. While it was a UK life tick the views were very distant and poor leaving me wanting more. Guess what? The views of the Severn estuary bird were very distant and poor leaving me wanting more – oh well third time lucky!!!!
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| Dartford Warbler, Thursley Common March 2019 |
In recent years I have had an annual spring date with Thursley Common in Surrey which boasts a number of heath and woodland specialists that are nigh on impossible to see in Oxfordshire. I normally go in late March or Early April but this was, of course, impossible this year. So on the late May bank holiday Monday I foolishly decided to brave the crowds and make up for lost time. One of the key species here is the aforementioned Dartford Warbler. At the location where there have been a number of territories in the past I was immediately greeted by their short somewhat hard on the ear song which belies their true beauty. Very subjectively, they seem to have done quite well over the mild winter with at least the same if not more birds than last year. The advantage of an early visit on a sunny still day in March is that the males will quite often jump onto the top of the gorse to sing. They are now well into the breeding season which raises two problems. Firstly, they are a lot more sulky in the undergrowth. Secondly, they are schedule one birds which absolutely must not be disturbed during the breeding season. I hence contented myself with glimpses of the birds fliting through the undergrowth as I walked along and did not pause for long so as not to disturb them. Having said all that, the heath became increasingly busy as the sunny bank holiday morning went on with numerous young boisterous families and dogs going to and fro near the birds. I do hope that these delightfully scarce warblers were not too disturbed.
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| Wood Lark, Thursley Common, March 2019 |
One of my other key targets for the day was the Wood Lark, a bird whose true beauty lies in its wonderful song delivered atop a tree or in an undulating song flight. Given a good view a silent bird is also ready identifiable even at distance by one of its key characterises, a rather comically short tail. I had three sightings which could have been the same bird and some lovely song but all a little too distant for photography. I also had a distant view of a Tree Pipit signing from the top of a dead tree – another year tick for me.
The Redstart is another bird that I would have expected to have seen by now so I walked to a wooded area where I have seen them before and saw a couple of very fine males. This is close to the famous spot where the paparatsi hunt Colin the Cuckoo. It was immediately obvious that he had survived the winter as there were twenty or so photographers present but I decided that this was not for me today, although I must confess to indulging in the past, and I did not delay long.
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| Stonechat |
Stonechats were fairly numerous on the heathland. The males have a number of characteristics to recommend them. In summer plumage they are very fine looking birds indeed and tend to be very confiding, often returning to sit atop a favoured perch to sing and survey their territory and will ignore you as long as you keep a sensible distance. There were already speckly juveniles begging for food from their parents. This again made me think of the benefits of residency in a warm winter. Compare and contrast to the Swallows in our horse stables which have only just stated repairing their nest in preparation for breeding.
I really struggled to get sharp images on this trip and started to think I had not mastered the complex autofocus settings of my new camera. When I go home I checked all my settings and discovered that at some point I had turned the IS off on the lens. No wonder the images were soft, there is no chance of handholding a heavy 700 mm lens at 1/500 second without image stabilisation – imbecile!
There are migration examples that I simply can not fathom. There must be an evolutionary advantage in the chosen strategy or Darwinism tells us that those adopting it will rapidly die out. I’ve mentioned the issue of African Nightjars before that really baffles me. There are a large number of Nightjar species in Africa. All but one are resident, our European Nightjar which migrates to Europe for the summer. This seems strange given that they are night feeders and the northern summer nights are short. I wonder what the evolutionary driver for this is when all the other resident nightjars clearly have ample year round food?
I inherited my lifelong love of gardening from my parents and grandparents, a beautiful gift for which I am eternally grateful. One of my grandfathers was the head gardener at a big estate near Blandford. My other grandfather had a large garden behind his cottage just up the road from the cottage I grew up in Hindon in Wiltshire. Both grandfathers fought in two horrendous wars which I’m very sure contributed to both being taken from us far too young. I have the most lovely childhood memories of growing up in the Wiltshire countryside with seemingly endless walks and hours spent ”helping” my grandparents in their gardens.
Prior to living in their Hindon cottage, my grandparents were the publicans of the Grosvenor Arms in the same village. I lived in the pub with my parents up to the age of 4. My parents told me that I was particularly fond of a sip of beer from the locals glasses, probably explaining another lifelong love of real ale. My parents, who are sadly also lost to me now, use to tell me a story of life in the pub. My grandfather use to take me down into the cellar and show me the barrels and there workings. One day I crept down there and had a go at changing the barrels on my own. He was not best pleased as he walked back up the hill to his pub to see beer pouring out of a ground level grill in the cellar wall. As a toddler I was quickly forgiven, my parents, however, were another matter!
I can’t remember a year like this in the garden, the wet very early spring followed by endless sunshine, and hence lots of watering, has produced mammoth growth on the fruit and veg. The greenhouse is a couple of weeks advance on the norm. The tomatoes are laden with rapidly ripening green fruit with all the delicious promise to come of picking and immediately eating sun warm tomatoes. The fruit seems to be on steroids with the raspberries, strawberries and blueberries absolutely weighed down with ripening fruit.
Our David Austin English roses and paeony flowers get wrecked in heavy rain but this year they are glorious. My time in the garden so far this year really has been the most wonderful antidote to the terrible horrors happening out there in the real world.
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